Prosthetic occluders for repairing intracardiac defects, such as interatrial and interventricular septal shunts, patent ductus arteriosus, patent foramen ovale, and occlusion of the left atrial appendage, are well known in the art. Moreover, systems for percutaneous transluminal front-end loading delivery and retrieval of a prosthetic occluder have been described. Representative is “System for the Percutaneous Transluminal Front-End Loading Delivery of a Prosthetic Occluder”, U.S. Pat. No. 5,486,193 (Bourne et al.), the entirety of which is expressly incorporated by reference herein, which discloses a complete system including a front-end loading portion, a control assembly, and an introducer.
Significant problems exist, however, with the front-end loaders currently known in the art. A first problem that may arise with current front-end loaders is the introduction of air into the indwelling introducer sheath when the front-end loader is introduced into the hub of the introducer sheath to deliver or retrieve a prosthetic occluder. Air that is introduced into a closed system, such as the introducer sheaths known in the art, may find its way into the patient's cardiovascular system, risking acute pulmonary embolism, myocardial infarction, stroke, and possibly death.
A second problem with current front-end loaders is that they are not well suited, should the need arise, for the retrieval of a prosthetic occluder from the heart or a vessel. Occasionally during a procedure to implant a prosthetic occluder in a patient, the occluder is an improper fit, deploys improperly, or is in some way damaged and must be retrieved from the patient. With current front-end loaders, significant problems often arise in attempting to collapse and withdraw the prosthetic occluder from the lumen of the introducer sheath into the lumen of the front-end loader. For instance, in withdrawing the prosthetic occluder from the lumen of the introducer sheath into the lumen of the front-end loader, the proximal portion of the prosthetic occluder may catch on the distal end of the front-end loader, potentially preventing removal of the occluder. For example, the prosthetic occluder may become snagged on the distal end of the front-end loader, necessitating the removal of the introducer sheath and the front-end loader from the patient in order to remove the occluder. In essence, the prior art lacks a reliable and efficient system for ensuring that the occluder can be withdrawn into the front-end loader so that the introducer sheath will not have to be removed from the patient.
It is, therefore, an object of the present invention to provide a front-end loader that minimizes or eliminates the introduction of air into an indwelling introducer sheath and that facilitates the retrieval of a prosthetic occluder without removal of the indwelling introducer sheath, should the need to do so arise.